A cruise control system is conventionally used in a motor vehicle with an internal combustion engine operative to maintain a set speed of the motor vehicle. If the motor vehicle is traveling over a level surface, that is to say a surface having neither a positive (climbing) nor negative (descending) gradient, with the cruise control system activated, a constant quantity of fuel is generally fed to the internal combustion engine. If the motor vehicle is traveling over a positive gradient, the cruise control system feeds a relatively large mass flow of fuel to the internal combustion engine, in order to adjust the speed of the motor vehicle to the set speed. As a result, the consumption of fuel is increased. If the motor vehicle is traveling over a negative gradient, the cruise control system supplies the internal combustion engine with a relatively small mass flow of fuel, in order to adjust the speed of the motor vehicle to the set speed by means of engine braking.
DE 102 05 226 A1 and DE 10 2008 061 392 A1 relate to a cruise control systems for motorvehicles.